Flash butt welding machines have been known in the past, and there have been attempts to control such welders by analog circuitry. One welding machine employing such an analog circuit is shown in U.S. Pat. No. 4,321,452 entitled "Flash Welders" issued Mar. 23, 1982 in the name of Deffenbaugh. That patent discloses apparatus for detecting whether or not the gap in adjoining ends of a ring-like workpiece to be flash welded is of normal size, or is so much larger as to produce an unsatisfactory weld. However, the apparatus is of limited value because it uses a surge in weld current in order to sense the condition of the weld. In addition, it relies on a comparison with platen motion and on detection of the presence of a weld. These techniques require a substantial period of time in order to stop a defective weld. As a result, improperly welded parts may be stuck together and have to be scrapped.
According, a primary object of the present invention is to provide improved techniques for assuring that a weld machine is in optimum condition for initiating a welding process, thereby improving the quality and accuracy of the resulting weld.
It is another object of the present invention to provide techniques for automatically and accurately checking whether the tap setting of a weld machine is proper for the part being welded.
Yet another object of the present invention is to provide an accurate technique for calibrating a part before it is welded in order to determine the electrical load presented by the part to the welding transformer.
Still another object of the present invention is to provide techniques for assuring that the ends of a piece to be welded are displaced by a predetermined initial welding distance.